LHC To Announce Its Lepton Universality Violation Results On Tuesday (20-Dec-2022)

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Since the last activity on this thread in March, 2023, newer experiments have shown a persistent discrepancy with the Standard Model (SM) in the rare Flavor Changing Neutral Current (FCNC) of a neutral B meson decomposing to a neutral kaon and muon/anti-muon pair. So, hopefully, this small crack is evidence for new physics beyond the SM.

https://physics.aps.org/articles/v19/94
 
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In the thread B ->s ##\mu\mu## there is a Feynman diagram illustrating this interaction, posted by mfb in the very first post. I'm trying to figure out how many weak vertices there are in this decay: ##B^0_s \rightarrow \phi \mu^- \mu^+##. Is it just 2 (either end of the wiggly Z line), or 4 if you count the intersections of the dotted line with the bottom straight line?
 
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Davephaelon said:
Since the last activity on this thread in March, 2023, newer experiments have shown a persistent discrepancy with the Standard Model (SM) in the rare Flavor Changing Neutral Current (FCNC) of a neutral B meson decomposing to a neutral kaon and muon/anti-muon pair. So, hopefully, this small crack is evidence for new physics beyond the SM.

https://physics.aps.org/articles/v19/94
The second to last paragraph of the most recent article linked in the linked source notes that the biggest discrepancy drops from 4.1 sigma to 0.2 sigma when the bin closest to the charm loops is removed from the analysis, and the charm loops aren't properly considered in this analysis. Essentially all of the other discrepancies are under 2.5 sigma and under 2.1 sigma when considering look elsewhere effects.

Given the particularly involved methods of calculating the SM expectation involved, and the fact that the uncertainties are estimated using "pseudoexperiments" which is not the usual means of doing so, I'm pretty skeptical that this has a BSM explanation. Also, the data set of 17,000 events is small enough to leave room for statistical flukes.
 
ohwilleke said:
The second to last paragraph of the most recent article linked in the linked source notes that the biggest discrepancy drops from 4.1 sigma to 0.2 sigma when the bin closest to the charm loops is removed from the analysis, and the charm loops aren't properly considered in this analysis. Essentially all of the other discrepancies are under 2.5 sigma and under 2.1 sigma when considering look elsewhere effects.

Given the particularly involved methods of calculating the SM expectation involved, and the fact that the uncertainties are estimated using "pseudoexperiments" which is not the usual means of doing so, I'm pretty skeptical that this has a BSM explanation. Also, the data set of 17,000 events is small enough to leave room for statistical flukes.
Thanks for responding, and the deep dive into the data. But I'm a bit confused, as I looked at the 2nd to last paragraph in the paper "Comprehensive Analysis of the [equation] Decay" (too tedious to write the equation with latex). I couldn't find the "4.1 sigma to 0.2 sigma when the bin closest to the charm loops is removed from the analysis". The paragraph I'm reading starts with the words "The flavio {94} and the EOS {95} software packages are used....". Nowhere does it say anything about sigmas in that paragraph. The previous paragraph does, but doesn't match the wording you wrote. I guess I have to look at the references?
 
The paragraph that I'm referring to is:

The flavio [94] and eos [95] software packages are used to fit the configuration (i) results, varying the parameter ℛ⁢𝑒⁢(𝒞9). For the flavio package, the default values of the SM nuisances are used, including QCD effects as in Refs. [13,27], while for the eos package, values are taken from Ref. [96]. The 3.3⁢𝜎 discrepancy with respect to the SM value of ℛ⁢𝑒⁢(𝒞9) obtained with flavio in Ref. [5] becomes 3.6⁢𝜎 ( 3.8⁢𝜎) with flavio (eos). Including the differential branching fraction, the discrepancy increases to 4.1⁢𝜎 ( 4.0⁢𝜎). Neglecting the 6.0<𝑞2<8.0  GeV2/𝑐4 bin that is closest to the charmonium resonances reduces the observed significance of ℛ⁢𝑒⁢(𝒞9) by about 0.2⁢𝜎. The best fit to the angular distribution is obtained with a shift in the SM value of ℛ⁢𝑒⁢(𝒞9) by −0.9⁢4+0.21−0.17 ( −0.92 ±0.23) with flavio (eos). When combining the information from the angular observables with the branching fraction, a shift in ℛ⁢𝑒⁢(𝒞9) of −0.9⁢3+0.18−0.16 ( −0.94 ±0.22) is obtained with flavio (eos). Differences between these numbers and those reported in Refs. [44,45], which fit for the Wilson coefficients directly, are due to the model inputs used, including the use of LHCb data to constrain the size of nonlocal contributions.
 
I see what the problem is. My computer didn't properly load the text. On my screen it says: "Including the differential branching fraction, the discrepancy increases to ( )." Then the next line starts with "Neglecting the bin which is closest to the charmonium resonances reduces the observed significance of by about ." Then it continues with: "The best fit to the angular distribution is obtained with a shift in the SM value of by ( ) with flavio (EOS)." And there's more deletions after that. I suspect that if I download the PDF that the text will come out fine. Also I'll close some, or most, of the 11 windows that are open. It's getting late here in the east, so I'll pick this up in the morning. However, I'm encouraged that the significance doesn't drop from 4.1 to 0.2, as you indicated in the earlier post, but is diminished by just 0.2 sigma.
 
That fixed the problem, the PDF came out fine, no errors. So the LHCb collaboration completed its third run in June, 2026 and will be analyzing its data, which is five times larger than the data set collected previously in the first two runs. I imagine physicists are eager to see what comes out; whether the anomaly trend continues or fizzles, like so many previous anomalies.
 
Davephaelon said:
That fixed the problem, the PDF came out fine, no errors. So the LHCb collaboration completed its third run in June, 2026 and will be analyzing its data, which is five times larger than the data set collected previously in the first two runs. I imagine physicists are eager to see what comes out; whether the anomaly trend continues or fizzles, like so many previous anomalies.
Flukes tend to accumulate in recent years, I wonder if there's more than statistical errors here involved here.
I mean as an amateur basketball player I once scored from an entire whole court; but it's not something that will repeat itself ever so often if you get my drift.
So if we want our physics theories to include every possible scenario in the universe perhaps we need to relax our postulates, like the speed of light being finite.
 
loop quantum gravity said:
So if we want our physics theories to include every possible scenario in the universe perhaps we need to relax our postulates, like the speed of light being finite.
Given the abundance of empirical evidence for finite light-speed, what does this statement even mean?
 
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loop quantum gravity said:
Flukes tend to accumulate in recent years, I wonder if there's more than statistical errors here involved here.
I mean as an amateur basketball player I once scored from an entire whole court; but it's not something that will repeat itself ever so often if you get my drift.
So if we want our physics theories to include every possible scenario in the universe perhaps we need to relax our postulates, like the speed of light being finite.
Erm, the speed of light has been determined to max out at 299,792,458 m/s. There has not been any evidence that light can travel faster in a vacuum.
 
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renormalize said:
Given the abundance of empirical evidence for finite light-speed, what does this statement even mean?
a decade or so allegdly physicists found a neutrino with a speed faster than the speed of light. After a few weeks they found a mistake in the experiment. At the time they did the experiment they glossed over this detail.
I don't understand, there cannot be an experiment that detect speeds faster than light? is SR and GR a religion of some sort?! that their postulates cannot be broken?
For me physics is always about the truth first, and not being a zealot of some religion (theory).
You can delete my opinion as it's not mainstream...
 
loop quantum gravity said:
a decade or so allegdly physicists found a neutrino with a speed faster than the speed of light. After a few weeks they found a mistake in the experiment. At the time they did the experiment they glossed over this detail.
I don't understand, there cannot be an experiment that detect speeds faster than light? is SR and GR a religion of some sort?! that their postulates cannot be broken?
For me physics is always about the truth first, and not being a zealot of some religion (theory).
You can delete my opinion as it's not mainstream...
The FTL neutrino was ruled out due to an error as you said.
The speed of light is a physical property of the universe, an empirical property like the mass of a proton.
It cannot be anything else.
 
loop quantum gravity said:
a decade or so allegdly physicists found a neutrino with a speed faster than the speed of light. After a few weeks they found a mistake in the experiment. At the time they did the experiment they glossed over this detail.
I don't understand, there cannot be an experiment that detect speeds faster than light? is SR and GR a religion of some sort?! that their postulates cannot be broken?
For me physics is always about the truth first, and not being a zealot of some religion (theory).
You can delete my opinion as it's not mainstream...
Plenty of guys on here will explain it better like @Ibix or @PeroK
I will add that the scientists of the time did not expect light to behave the way it did, if you look into some of the experiments.

The community was taken where the evidence led them, expectations and postulates are not the same as blind faith.
 
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loop quantum gravity said:
that their postulates cannot be broken?

They can in principle, but they were not in any experiment done to date. And we see no reason for them to be broken. What's your point? Because I don't get it.

loop quantum gravity said:
a decade or so allegdly physicists found a neutrino with a speed faster than the speed of light. After a few weeks they found a mistake in the experiment. At the time they did the experiment they glossed over this detail.

Yes, and? Again, what is the point of bringing that up? The mistake was a loose cable. It's a technical mistake, not that the experiment was done in a wrong way.